1. Field of the Invention
The present invention relates to a sound amplifying apparatus for amplifying sounds or voices picked-up by a microphone and delivering amplified sounds or voices through a speaker, and more particularly to a sound amplifying apparatus having howl-suppressing capability.
2. Description of the Prior Art
At a lecture or the like using electro-acoustic; appliances such as microphones and speakers, howling often occurs when the lecturer moves or if the condition in the hall changes. The "howl" is an undesirable prolonged sound produced because of acoustic feedback. In case howling occurs, the acoustic adjuster ("mixer", hereafter) either lowers the sound signal level in the frequency hand in which the howl would be occurring by means of a graphic equalizer, or lowers the entire output level. When the howl is suppressed or the position of the lecturer is changed, i.e., when the condition of sound pickup varies, the mixer returns the characteristic of the graphic equalizer or the entire level to the original characteristic or level. Every time a howl occurs, the mixer repeats this action to suppress the howl.
In such constitution, however, when a howl occurs, the mixer must always lower the frequency of the graphic equalizer, so that it takes labor to suppress the howl. Also, since the frequency band for lowering the graphic equalizer cannot be instantly and accurately known, and it takes time to suppress the howl.